The present invention relates to a method of coating, and, more particularly, to a method of applying a coating material to a strip of metal or other substrate.
Currently, numerous methods exist for applying a coating or thin film of material to a strip of metal or other material. One conventional method of coating a continuous strip of substrates is to submerse the strip in a bath of the coating material. This can be accomplished by pulling the substrate through the bath of coating material, and then wiping off any excess coating material. This method has many drawbacks. One drawback to this method is the difficulty to control the amount of coating material applied to each side of the strip. Another drawback is the inability to apply different coating materials to each side of the strip. Also, this method often wastes a certain amount of the coating material during the wiping step.
Another known method of applying a coating or thin film of material to a strip of substrate is to employ a spray coater or atomizer. In such a method, the coating material is electrostatically disposed on the strip. A spray coater in accordance with this method is disclosed in U.S. Pat. No. 4,839,202.
Other known types of coating methods include passing the strip of substrate through various applicators which deposit a thin film onto the strip with or without electrostatic assistance. The applicators can be either stationary members or rotable members. One example of such a coating apparatus, which uses a pair of oppositely-disposed applicators, is disclosed in U.S. Pat. No. 5,549,752 to Hahn et al. The Hahn patent discloses passing a continuous strip of material between a pair of oppositely disposed applicators for applying a thin film thereto. In one embodiment, two stationary wicks directly contact the sides of the continuous strip of material to apply a coating to both sides of the sheet material. In another embodiment, the wicks apply the coating material to two feed rolls which contact the sides of the strip to apply a thin film of coating material thereto. One drawback to this type of coating apparatus is that it lacks the ability to adjust the amount of coating material being supplied to various sections of the applicators.
Other examples of prior coating apparatuses are disclosed in U.S. Pat. Nos.: 5,985,028 to Cornell et al.; 4,601,918 to Zaman et al; 4,604,300 to Keys et al.; 4,712,507 to Helling; and 4,995,934 to Janatka.
There is a need to improve upon the known coating methods to increase efficiency, accuracy, dependability and safety and to decrease costs and waste. Accordingly, it is an object of the present invention to provide a method of applying coating material to a strip of substrate that enables precision control and efficient operation thereof. It is a further object of the present invention to provide such a method that enables the application of coating to the strip in a high speed manner. It is a further object of the present invention to provide such a method that also eliminates or reduces waste.
These and other objects of the present invention are achieved by providing a method of applying a coating material to a moving strip of metal or other substrate comprising the steps of: (a) providing a signal from a controller to a coating supply unit to control the passage of coating material from the coating supply unit through a liquid usage detector and a liquid meter unit and to a coater, desirably at a constant pressure, for application to the moving strip; (b) providing a measure signal from the liquid usage detector to the controller to measure the flow rate of coating material through the liquid usage detector; (c) providing a delivery control signal from the controller to the liquid meter unit to control the amount of coating material delivered from the coater to the moving strip; and (d) providing a dispense signal from the controller to the coater to dispense coating material from the coater for application to the moving strip. In a preferred embodiment, the method desirably also includes the steps of detecting the position and width of the moving strip and providing a position/width signal to the controller to control the positioning of the dispensing of coating material by the coater. The method also may include the step of recovering excess coating material dispensed from the coater.
Other objects, advantages and novel features of the present invention will become apparent from the following detail description of the drawings when considered in conjunction with the accompanying drawings.